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MHT CET · Physics · Waves and Sound

Two identical wires are vibrating in unison. If the tension in one of the wires is
increased by \(2 \%\), five beats are produced per second by the two vibrating wires.
The initial frequency of each wire is \((\sqrt{1 \cdot 02} \doteq 1 \cdot 01)\)

  1. A \(1000 \mathrm{~Hz}\)
  2. B \(500 \mathrm{~Hz}\)
  3. C \(400 \mathrm{~Hz}\)
  4. D \(200 \mathrm{~Hz}\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(500 \mathrm{~Hz}\)

Step-by-step Solution

Detailed explanation

\(\mathrm{n} \propto \frac{1}{2 \ell} \sqrt{\frac{\mathrm{T}}{\mathrm{m}}} \quad \therefore \mathrm{n} \propto \mathrm{T}\)
\(\frac{\mathrm{n}_{2}}{\mathrm{n}_{1}}=\sqrt{\frac{\mathrm{T}_{2}}{\mathrm{~T}_{1}}}=\sqrt{\frac{1.02 \mathrm{~T}_{1}}{\mathrm{~T}_{1}}}=\sqrt{1.02}=1.01\)
Also \(\mathrm{n}_{2}-\mathrm{n}_{1}=5\)
\(\therefore 1.01 \mathrm{n}_{1}-\mathrm{n}_{1}=5 \quad \therefore 0.01 \mathrm{n}_{1}=5\)
\(\therefore \mathrm{n}_{1}=\frac{5}{0.01}=500 \mathrm{~Hz}\)
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